Gig in the wild

Discussion in 'Miscellaneous [BG]' started by Probiotyk, Aug 22, 2021.


  1. Probiotyk

    Probiotyk

    Aug 22, 2021
    I have been using the forum as a main font of knowledge for a couple of years now, and now came the time to register and ask a question myself, so hello world!

    The problem I need to solve is playing outdoors (by the sea, in a field etc). Since it's not exactly gigging, I'm only interested in acquiring a power rig that would be sufficient to power my 120W combo amplifier and possibly a couple of effect pedals.

    I have looked through this forum and some other places on the net, but haven't managed to find a guide for dummies - most of the material was using some presupposed knowledge that was difficult for me to parse in order to learn in digestible chunks. I ask for patience as I imagine quite a few basic questions will be posed in this thread, starting with the following:
    • What information do I need in order to correctly estimate the power consumption of the amplifier I own for supposed "x" hours of unbroken playtime?
    • Can I buy a power source (supposedly a battery?) and plug the amp directly into it, or is it necessary to put something in between the powersource-amp chain?
    • If I need to buy something besides the power source, how will it influence (if at all) the requirement for capacity of said power source?
    • How do I convert the information from the first question into information regarding the desired capacity of the power source?
    More questions are sure to pop up in time as for now I don't even know what I need to know about. I purposefully left out the details, since I imagine a skeletal/101/for dummies guide to the general concepts might be useful for someone wanting to learn in the future.
     
  2. el murdoque

    el murdoque

    Mar 10, 2013
    Germany
    Most of the answers vary with the equipment used, that is why a general guide will not really work.

    The two most important questions are:
    -What is the exact amp you want to power?
    -What is the budget you imagine?
     
    Wasnex likes this.
  3. Hi, Probiotyk, and welcome to the forum! I don't know anything about this kind of power sources, but I know about this:

    upload_2021-8-22_12-8-32.png

    Roland Micro Cube bass amp. Works either plugged in or on batteries. It has some built-in effects, like delay, flanger, etc. Also a tuner and a drum computer. I think there are several threads about it here.
     
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  4. Probiotyk

    Probiotyk

    Aug 22, 2021
  5. el murdoque

    el murdoque

    Mar 10, 2013
    Germany
    Define unbroken playtime ... when you send a 100Hz sine wave through the rig, your playtime will be a lot shorter than when you play bass. When you max out the amp, you will get less playtime. When you max out the bass EQ you get less playtime.


    You can do that when the amp accepts the voltage the battery provides. An example is the Phil Jones Double Four, which runs at 19V, which can be provided with a laptop battery.
    You can not do that if your power requirements exceed the voltage the battery provides. In those cases you need to plug in a voltage converter - and most likely you need to convert AC/DC, too.



    Well, a converter will cost you a few amps along the way, which depends on the quality of the unit.


    Basically, if you hook up a battery to a voltage converter and feed that into a combo amp, it either works or it does not. The more current you draw, the faster the battery is drained. The bigger the battery, the longer it takes.
     
  6. hrodbert696

    hrodbert696 Moderator Staff Member

    While I don't have an answer myself, I'd suggest asking this question in the Amps forum. That's where it's most likely to attract the attention of the TBers who would know.
     
    12BitSlab and CryingBass like this.
  7. el murdoque

    el murdoque

    Mar 10, 2013
    Germany
    The amp you linked is the European 230V version. Is that the case?
    This is important info, because TB has lots of participants from places that run 110V mains.
    You can imagine that this might lead to confusion and possibly broken gear.
     
  8. Probiotyk

    Probiotyk

    Aug 22, 2021
    I guess I would like to assume playing with the dials fully blown out for about 4hrs, unless that requires a battery the size of a fridge.

    Do you mean that the amp will degrade with a converter, or that the converter costs a lot?

    Thank you for being vigilant :) yup, it's european: "220/240V 50/60Hz Fuse T1A" is the only seemingly relevant information I found printed on the unit.
     
  9. el murdoque

    el murdoque

    Mar 10, 2013
    Germany

    Sorry, with amps, I meant amperes, not amplifiers. Whenever you convert one voltage to another, you loose a bit of battery runtime in the process. Those things do not operate without loss. You can expect the current draw of a 120W amp to be a bit below 100W when you run it loud (mind, this is a ROUGH estimate).

    The obvious thing to do would be a car battery plus converter.
    Car batteries are easily available and they provide a fair bit of voltage and stamina.
    The thing is the converter.
    I've tried a few. Never to play bass, but to run 230V things in camping and boating environments.
    If you go cheap on the converter, you won't get the juice needed, might shorten the battery life and you loose a ton of run time to the converter.
    If you go for a good one, you can expect to pay north of 250 bucks, so the converter alone costs as much as a Roland Cube amp.
     
    Wasnex likes this.
  10. Probiotyk

    Probiotyk

    Aug 22, 2021
    Well damn, haven't expected this level of problem complexity. Guess I gotta do some soul-searching now. Thanks so much for claryfing the topic for me!
     
  11. CryingBass

    CryingBass Ours' is the only Reality of Consequence Gold Supporting Member

    Apr 8, 2016
    Nothing great in life is easy. You will figure it out, and you have a ton of guys around here for some great advice.

    Welcome to TB.
     
    bassdrummer likes this.
  12. I don't recall batteries being requirement, at least in the first post. In the USA, I'd recommend a Honda Eu2000i inverter/generator. It has plenty of power, is quiet and portable. And instead of recharging, you just add more petrol. I'm sure there's European equivalent. I know Yamaha has a line of them.
     
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  13. DirtDog

    DirtDog

    Jun 7, 2002
    The Deep North
    Basic physics.

    I = P/V. In your case, 120W/240V= 0.5A.

    You need a power supply that can handle 0.5A. This is trivial for an AC power supply like a gas generator. Perhaps not trivial for a DC power supply like a battery.

    If you want to use a battery, you’ll need an inverter (battery is DC, your amp is AC).

    Big question is: can a 12V DC car battery, with an inverter, give you 0.5A AC?

    if you want to play for 4 hours using a battery, you need 4.0h x 0.5A = 2.0Ah (amp-hours) capacity…not accounting for any loss in the DC to AC conversion (using an inverter).

    Here’s a useful site to generate the info you need if you want to use battery as a power supply:

    Calculate AC to DC Amperage Through Inverter | BatteryStuff
     
    Last edited: Aug 22, 2021
    Jonny Reese likes this.
  14. MrLenny1

    MrLenny1 Supporting Member

    Jan 17, 2009
    New England
    1000 Watt Honda generator.
     
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  15. kesslari

    kesslari Groovin' with the Fusion Cats Staff Member Gold Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    DirtDog likes this.
  16. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    I've done some street playing using regular AC powered guitar and bass amps. The power source was a large battery, I think a marine battery, driving a voltage inverter that changed the 12VDC into 110VAC. The battery and converter weighed more than the amp I using (an old 60 W Crate combo). But it did work.

    So the minimum you would need for your AC powered amp:

    -- large 12V battery for motorcycle, boat, car, etc. Plus a battery charger of course.
    -- DC to AC power inverter large enough to handle your amp's power draw. For your 120W amp, I'd suggest 250W rating.
    -- Optional: a voltage regulator to make sure the AC voltage to your amp is clean and steady. See Furman AR series, in the USA they sell new for $600 and up.
     
    DirtDog likes this.
  17. The Roland Micro Cube is the cheaper option by far. Less than €260 at Thomann.

    Edit: not just cheaper, also simpler.
     
    DirtDog likes this.
  18. MichelD

    MichelD

    May 19, 2014
  19. Wasnex

    Wasnex

    Dec 25, 2011
    Sorry if this is too technical, but it's really the only way to gain the understanding you are asking for IMHO.

    I am by no means an expert on this, so hopefully if I wrote something that is wrong, one of the more educated people will offer a correction. I do have a background in electronics repair, and I did a bit of research to inform my opinions. In particular I read relevant parts of this webpage: Battery Basics - Guide to Batteries | BatteryStuff

    Ultimately the best you can do is probably develop sort of a crude estimate, because the necessary data needed to get a precise answer is either unavailable or too hard to find. But I will try to explain enough of the particulars so you have some idea how you would go about developing the estimate.

    You need a power source that can supply at least the max current the amp will be expected to pull (peak current). This is to prevent damage and or intermittent service, because the power source may go into protection mode if it senses an overcurrent situation.

    Often the amps current draw is not published. If the amp has a mains fuse, the fuse rating provides conservative estimate of the peak current, and AFAIK will give you a bit of headroom. The fuse is designed to blow when the amp fails, not when it is operating properly. Personally I think it's good to have a power source with a peak current rating that is at least double what the amp will pull...but I tend to go a bit overboard on stuff, so it's probably overkill.

    The next bit of information you need is the average power/current the amp will pull. Music is dynamic, so the amp does not ran at peak power continuously. The power source must be able to supply the average current the amp draws on a continuous basis. Unfortunately most amps don't provide any data related to this either. AFAIK the average power an amp draws varies by design. Class D is more efficient and I believe it typically pulls about half it rated power on average when pushed hard. Older class AB designs are less efficient and will pull more power when they are cranked.

    (See AC formula wheel below) The relevant formula to find current (I) if you know the power (P) and voltage (V) is I=P/V. So at 50W and 240V, we have I=50/240=0.208A. This is the amount of current the power source must provide if the amp pulls 50W. Or at 120V (I=50/120V=~0.417A) FYI I use ~ to indicate a rounded figure.

    upload_2021-8-22_14-27-22.png

    The Jackery power source I will discuss has a 25.2V battery. Due to losses in the voltage conversion process the battery will actually need to provide a bit more than 50W, but for the sake of our initial calculations, let's assume conversion is perfect and there are no losses. So, the power provided by the battery is still 50W, but the voltage and current are different. When you hold power constant, the voltage and current have an inverse relationship; so if one goes down the other must go up.

    We want to know how much current is necessary at 25.2V to give 50W. Again we will use I=P/V. I=50/25.2=1.984A. This is the amount of current the battery must provide if the amp pulls 50W and conversion is 100% perfect.

    The final part of the puzzle is the Watt Hours (Wh) and/or Amp Hours (Ah) of the battery. These figures will give you a ballpark of how long the battery can supply the average power you need. However, you need to understand that conversion from the DC battery voltage to the AC voltage you need will incur some losses. I think the better inverters are 90-95% efficient with the conversion, but I could be wrong. At 90% efficiency, the battery will need to provide 2.204A. (1.984/0.90=~2.204) This comes out to 55.552W. (~2.204x25.2=55.552).

    Something else you need to know is the capacity of the battery varies with how fast you pull the power out. In this context, the Wh and Ah are specified in regards to how much current the battery can supply steadily over 20 hrs. For example I am looking at the spec for a Jackery 1500 Jackery Explorer 1500 Portable Power Station . The battery capacity is 1534Wh and 60.9Wh. For the steady current the battery can supply continuously for 20hrs, divide by 20. 60.9/20=3.045. I believe this goes for the Wh as well (1534/20=76.7). So the Jackery 1500 can supply 76.7W continuously for 20 hours.

    If you pull the power out faster, the total available Wh and Ah goes down. The specs say the Jackery 1500 is rated for 1800W continuous /average, and 3600W peak. But keep in mind the battery is rated to provide 1534Wh total over 20hrs at 76.7 watts per hour. So at 1800W continuous, the battery will be depleted in less than one hour, and the total Wh will be less than 1534.

    Let's assume your amp pulls 100W average. If we assume the available Wh remains constant we would expect 1534/100=15.34hrs of run time. But remember the battery is rated to provide only 76.7W continuously for 20hrs. Since we are pulling the power out faster than this, the actual Wh available will be less than 1534.

    If we assume the amp pulls 50W average and the battery supplies 55.552W (1534/55.552=27.61hrs). Note the average power being consumed (55.552W) is less than the battery can supply continuously for 20 hrs (76.7W), so the available Wh will be more than 1534, rather than less. So if the amp is pulling only 50W, you should get more than 27.61hrs of run time.

    To get a better estimate you need specs for the battery. Many batteries have datasheets with a table showing how the total available Wh or Ah varies with the load. There may also be formulas that can be used to derate these figures, but I do not know them.

    I have made quite a few posts specifically on this subject. You can find some of them using the search box with the terms "Ah" and "20" with my handle "Wasnex" in the Posted by Member box. Also this post from @agedhorse is really great IMHO: Power for amp at outdoor gig

    Additionally I personally recommend that you pay a little extra and get a power source that provides a pure sine waveform, rather than modified sine. My understanding is pure sine can result in quieter operation, and some amps do not work well on modified sine.

    I have also made quite a few posts related to battery powered amps that you may find useful.

    Good luck!
     
  20. 5andFretless

    5andFretless Supporting Member

    Dec 18, 2007
    Long Island Ny
    My performance partner and I are routinely booked into gigs where the customer wants us in a gazebo or tent far from power. Since we advertise as an acoustic act they assume we don't need power. Unfortunately, my bass always need amplified, his guitar normally needs it, and our vocals also generally need amplified. Our solution is a small Honda EU 2200 generator that we try to place as far away from us and our audience as possible. Generally it isn't noticed since it is so quite to start with. Put it behind the tent, or around the corner of a nearby building and it disappears.
     
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  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 19, 2022

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